A conventional rotary electric machine comprises a stator coil formed by connecting sequentially a plurality of U-shaped conductor segments which are respectively inserted into slots provided in a stator core (for example, refer to U.S. Pat. Nos. 6,249,956B and 6,530,140B corresponding to JP3118837B, called Reference 1 hereinafter).
Each of the U-shaped segments of this rotary electric machine is set to an annular twisting tool in the state that straight portions of the U-shaped segments are arranged in a radial direction of the twisting tool, and a pair of the straight portions of each U-shaped segment are sheared inversely to each other along a circumference of the twisting tool, before the U-shaped segment is inserted into the slot. These twisted U-shaped segments are inserted into the slots of the stator core, and tip portions of these U-shaped segments protruding from the stator core are folded in the circumferential direction of the stator core, then are connected to each other to form a stator coil having a predetermined winding specification.
As a method to manufacture the U-shaped segment described above, it is known to cut a single wire rod into predetermined length and to bend the rods into U-shapes (for example, refer to U.S. Pat. No. 6,314,780B corresponding to JP2001-045721A, called Reference 2 hereinafter). In this method, an excessive bending preventer retains a turn portion in bending the rod, so as to prevent excessive bending and fractures of the insulation coating on the wire.
In the case that the U-shaped segments are manufactured by the method disclosed in Reference 2, the width of the U-shaped segment extends at the turn portion thereof by the size of the excessive bending preventer. Therefore, if a number of the U-shaped segments are inserted into one slot of the stator core, an end portion of the stator coil composed of the turn portion bulges in a radial direction of the stator. For example, in the case that a part of the stator coil is composed of four large and small U-shaped segments arranged in the radial direction of the stator, the size of the turn portion of each U-shaped segment is larger than that of the straight portion in the radial direction. Thus, if the straight portions are inserted in the slot to occupy most of the space therein (if the straight portions are installed in the slot in a radial direction of the stator so that the clearance therein is quite small), the turn portion bulge in the radial direction to center (or to perimeter) of the stator.
If it is prevented to interfere the projecting turn portion with the frame arranged around them (or with a rotor arranged inside of the stator), it becomes difficult to make the rotary electric machine in a small size. To incline the laminated turn portion to the radial direction of the stator, it is required to add a step to bend the turn portion, and the manufacturing step becomes complicated and undesirable.
It is thought to reduce the bulging volume by shifting the turn positions of four U-shaped segments in the inserting direction thereof from each other. In this case, however, it becomes difficult to make the rotary electric machine short in the direction of rotating axis, and electrical resistances of the U-shaped segments are dispersed. Thus, it is also difficult to adopt this method.